Piteously is how someone cries, begs, or looks when the pain and sadness make you feel pity. It is the adverb of piteous: not a new idea, just the “in that way” form. Like piteous, it sounds a little literary. A child may weep piteously in a story; a friend in real life more often just sounds upset. Though actually, it describes the manner of the suffering, not a small amount of it — it is not “a bit sad.”